Sodium refining of petroleum oils



Patented Oct. 21, 1952 SODIUM REFINING OF PETROLEUM OILS Byron M. Vanderbilt, Westfield, N. J assignor to Standard Oil Development Company, a corporation of Delaware N Drawing. Application May 1, 1950, 1 Serial No. 159,380

7 Claims.

l 1 This invention relates to a process for refining mineral oils. The process is particularly directed .to removal of gum forming substances, to the desulfurization or sweetening of oils, and to the color improvement .of oils. The process consists of a treatment of the oil to be refined with a treating agent consisting of finely divided metalesses are known for improving the quality of mineral 'oils, These processes are generally dire'ctedto improving one or more characteristics of the oil so as to produce superior oils. For example, in the refining of gasolines, itis 'fre: quently desirable, or necessary, to improve the odor oithe gasoline by sweetening the gasoline so as to remove malodorous mercaptans, or so as to convert them to compounds which do not have an objectionable; odor. Again refining processes are used to increase the resistance of the oil to oxidation, decreasing the tendency of the oil to form objectionable gum deposits in storage and transit. The process of this invention is, therefore, directed to this general field, in which petroleum oils are refined in a manner to improve the characteristics of these oils.

Th process of this invention is of general app'licationto petroleum oils, being suitable for the refinement of gasolines, heating oils, diesel fuels and so on. Howevenit is presently contemplated that theprocess is of principal importance as applied to the refining of gasolines and particularly of thermally or catalytically cracked gasolines. Asapplied in this manner the process of this invention provides a simple one step refining. process capable of providing a stable and sweet gasoline having good engine cleanliness characteristics. [This process is particularly advantageous since no caustic treatment or redistillation of the gasoline or petroleum fraction treated is required after the sodium-activator refining treatment.

Most broadly, the present invention may. employ eithersodium, potassium, or lithium in combination with a suitable activator Thus, ex

periments have indicated that any one of these three metalsmay be employedbut however, for economic reasons, the use of sodiumis to be preferred. Furthermore, the greater activity of pow tassium creates additional hazards in the bane dung or this metal. However, while this inven 2 tion will be described with particular reference to the use of sodium, it is to be understood that other alkali metals may be employed.

It is essential in the conduct of the process to be disclosed that the sodium employed be in a finely divided form. Thus, as will be brought out, it is' necessary that the sodium be inthe form of fine particles having a particle size less than about .50 microns in diameter. ,Improved results are obtainable when the particle sizeis even smaller than this, as for example, less than about 30 microns and even in the range of about 2 to 10 microns. Suitable methods for obtaining sodium in such finefparticles are known toflthe art. For example, sodium may readily be dispersed in a suitable vehicle such as-a hydrocarbon oil by heating a mixture of sodium andthe vehicle to a temperature above the melting point of the sodium andthenthorou'ghly agitating this mixture. High speed agitators, *homogenizers, colloid mills, or similar types of shear action dispersers are preferably employed to disperse the molten sodium in the form of very fine particles through the vehicle. The vehicle to be used may consist .of virtually any hydrocarbon oil. but is preferably a high boiling gasoline fraction substantially free of olefinic materials; -A vehicle which has been found to be entirely suitable isla petroleum fraction boiling in the range of about 3.00 to400 F. and consisting of a virgin naphtha. In order to maintain the sodium in the form of a stable dispersion of fine particles in such a vehicle, it is preferred that a dispersing or stabilizing agent be employed. Again, agents of this nature are known to the art and may consist for example of a resinous polymer or materials of a soap like nature such as sodiumoleate for example. p i

It has been, foundthat several different types of activators may be used in conjunction with the finely dividedsodium to secure the desired refining results.- Thus, as disclosed in U. S. application 107,383 formerly referredto, it had been found that secondary andtert'iary alcohols are suitable activators. It has now been foundthat ketones. and others are also suitable as activators and in some cases are to be preferred to the use of alcohols. Of the ketones, acetone is outstanding and is materially better than methyl ethyl ketone, methyl isopropyl ketone and methyl isobutyl ketone. Of the others, isopropyl other has been found to be the best although other ethers such as ethyl ether, normal propyl ethenisobutyl ether, secondary butyl ether, benzyl ether, and various mixed ethers may be employed. As a class the aliphatic ethers having four to ten carbon atoms are preferred.

In conducting the process of this invention it isgenerally preferred to prepare the dispersion of sodiumin a suitable vehicle and then to add 3 this dispersion. of sodium togetherlwithnthe .aotie vator to-thezoil to be refined. The actual treat ing process of the oil with the dispersion of sodium and the activator is simply conducted by agitating the mixture in the liquid phase at a suitable temperature.

employing secondary or tertiary alcohol, it:is suit-'-- able to use temperatures above about 150 C.

although preferably above about 200 C. and ,be-'

low about 250 C. In 'the case of ketones, the temperature may be inthe range of 200. to 225. C. and the. temperature of about225C." is preferred. Ethersare ineffectivebelow about 150 C. andare. particularly suitable f0r;use' at about 200? C1. or, higher. Itlhas been .f'o'und'thatmaterially improved; results may. be. secured'fby em.- ploying. critical temperatures. fora given. refining efiectl Thus, in the caselofhsulfurzremoval; optimum. results are ,obtainedsby; refining ,at a temperature inthe. criticalv range. ofrllabout' 200?- to 225- C. v

Although there: is a. minimum. temperature at which -;sodium. and augivem activator-sis. efi'ective, theres is also a, maximum temperature. above which inferior results-areobtained... Thisfis well illustrated from: a series, of: thermal naphtha treatinglruns .whichwere carried out using one per. cent of sodium, 6,- microns average particle size, .and-: lo moleperi cent of isopropanol as actie vator: Thedataarespresented in the following tables,-

7 l L I ASIM Coupe-r Temperature: 'Iimca- DEDE' Break-1 Dishv down Gum'- Ho'1r1s ControLmo'treat .I.-. 021146; 5516 1601 v 260' 93 CH" 1 0.127. 39. 6. 365 l0, 200C 1'" 0.'01"- 1250" 480 l.-3 225. V2 0g021'" 11123 4 4:15' 4. 7 250? M 0 0.1015 10. 7 I 605 9. 7 275 6 0.0a 13.}6 265" 152 30090 0.006 21-..4' I 90 99":

i 1 Diazonium'fiuobotate deposit Jfactor;

It may be observed that as' th'e =t'emperatureis increased to about-200- the removal of sul-fur-be- 0 comes much more effective, accompanied with generally-better refining results than at-90?"C. In going to higher temperatures than 200 6;, the-copper dish-gum values increase: In going to temperaturesof the-order of 275-300" C.,' properties other than sulfur content; seriously dete riorate; Based' onthese *and other data-it would appear' that the optimumtemperance range -in order-to get best' overall improvement is in the range-of 200-250 C. Similar 'datafor sulfur-removal from catalytic-naphtha are given below whentreated-with 1% ofsodium (2-6 microns diameter) and 10- mole-per centof isopropanol as activator:-

The; temperature" to; beemployed is most broadly a temperature above about 150 0. although it is necessary thatfa' more' As indicated, therefore,.,the. refining, process of thisiinvention consists of agitating; a-mineral oil to be refined with a fine dispersion of sodium in the presence of an activator such as, acetone or isopropyl ether.

The concentration of sodium to be-employed is'inthe range of about 0.25% to 2.0% and is preferably about 0.5 to 1.0% by weightrbasedxon the mineral oil to be treated. As.inclicated; the sodium is preferably added in the form of a dispersion in a suitable vehicle and the contentiof the sodium in this vehicle may be upto-about by weight or somewhat greater. The-quantity of activator to be employed may be about 5 to 30 molar percent but is preferably 5 to .10.mol per cent, based on the amount of sodium used." The minimum amount 'of"'activator"is"de termined largely bythe quantity necessary to stabilize the "sludge formedin' a finely "dispersed condition;- V

The' refining process" does n'ot appeart to" be greatly influenced by, pressure althoughdt" is es?- sential that suifi'cient pressure be employed to maintain the" reaction system 'in' the liquid'phase'. The time required 'tosecure" a: suitablerefining effect is about hour,although somewhat'short, er onionger periods may be employed depending upon the temperature maintained.

After agitation under the indicatedrconditions, the mineral oilcan readily be separated fr'om the refining agents employed anol the. residues of these agentsbya simple filtration process carried out below about 50 C. The efiect of such a filtration is. to remove sludge ,formedjduring' the treating process together. with otherldeleterious productsrformed" during the treatment. It'li'as been, determinedhthat while filtration, suitably purifies thetreated. mineral oil when conducted below about 50"CL, filtration above C. isnot efiective While filtration. at higher temperature isv effective to. remove any sodi'umpresent, such filtrationis not effective inremoving other un.- desired constituents with. the. result that there:- fi'nedjoil product shows little improvement-(over thetoilubefore, treatment. It is ,tolb'e understood, therefore, that filtration, of. the reaction mixture after. thev refining process. hasbeen'. carried. out must beconductedat temperatures below about 50v C. When carriedout in thismanner no fur: ther treatment of. the refined-Foil is, required. For example, it is notnecessary. to-wash' .or distill thisoil. However in. the case of higher. boiling oils suchas heating oils, which may contain acid materials-such as naphthenic acids. and'certaiii phenols, it maybe necessary to follow the filtration with awater oracidbwash to remove oil "solu' blesodiumsalts.

In. orderto Indy, evaluate the process. ofiifthis invention a series of experiments were conducted inwh'ich' the different process variables were explored. In these: tests avarietyof inspections were" employed to determine the improvement secured bylthe particulartr'eatments: One test employed'was an oxidation stabilitytestwhich'is identified herein" as the AS'I'MBreak-Down Test; This test'is'specifically'ASTM Test B52546!- A third test" which was "carried' out is" known as the" CopperfDish Gum Test and indicates-*the gum" content of" the petroleum oil: in" Jug/ cc: as "obtained by; heating the petroleum-' oil iat 212"F. in"-a"copperdish. Stillanoth'er test'employed "was the Doctor Test which utilizes plumbite and a trace" of free sulfur to 1 indicate the presence or absence of 'mercaptans:-- Results of this testare indicated as pass or did-not-pass" corresponding to the absence or presence? re=- emission photometer.

225 C. was very advantageous.

"spectively of mercaptans. Finally the last test employed to evaluate results was a test givin what is knownas the diazonium fluoborate deposit factor. This test indicates the engine cleanliness characteristics of gasoline. The test utilizes the coupling reaction which takes Place between diazotised p-nitro aniline and certain unsaturated compounds (which cause engine fouling) to form a colored compound. Intensity of color formed aftera given time intervalis taken as an index of the deposit formingcompounds present. In running the test the faction of the sample boiling over 2751B. and-purified 'by treatment with dilute acid and, alkali and steam distillation to 3% bottoms is used. A known quantity of this fraction is added to a solution of p-nitro-aniline diazonium fluoborate (NOzCsH4N=NBF4) in acetone and theoptical density measured at intervals in a. Hellige-Diller The optical density is plotted against time and the value after 20 minutes read from the curve. The optical density multiplied by the ratio of the fraction boiling over 275 F. to the whole sample gives the diazonium deposit factor.

Results obtained by these tests are indicated hereinafter making reference to the inspections identified above.

EXAMPLE 1 Four hundred grams of thermal naphtha obtained by thermal cracking of reduced crude was mixed with four grams of finely dispersed metala lie sodium in 4.5 grams'of virgin naphtha boiling in the range 320-380" F. The mixturewas then heated at 90 C. for one'hour, cooled to 40 C., and the sludge and unreacted sodium removed by filtration. The filtrate was inhibited with the conventional inhibitor, N,Ndisecbutylparaphenylenediamine, in concentration of one pound per 5000 gallons and was then submitted to the evaluation tests indicated in Table 1.

EXAMPLE 2 This run was as in Example 1, except that 1.82 cc.of isopropyl ether was employed and the mixture heated at a temperature of 225 C. for

one-half hour in a pressure bomb.

EXAMPLE 3 Example 2 was repeated except that "the isopropyl ether was omitted.

- Evaluation data from these three runs include the following:

Table 1 ASTM Copper Run Breakish 5 gg gg down Gum Control 160 12.9 0.146 55. 6 Example 1... 165 62 0.142 50 Example 400 2 0.015 10 .Example 3 240 16 0.112 v 33 Diazonium fluoborate deposit factor.

Referring to the table indicating the results of Examples 1, 2 and 3, it will be observed that the use of isopropyl ether at a temperature above Thus, comparprovided little or no refining efi'ect.

temperature as shown by Example 3 since finely dispersed sodium alone without the isopropyl ether as shown by Example 3 even at the temperature of 225 C.'does not provide an equivalent refining effect. It may be noted that as yet the mechanism of the activation effect contributed by the ether is not understood, although experiments have indicated that at about 200 C. there .is a slow reaction between the ether and sodium to form a white substance. The comparison of Examples 1 and 3 to the control inspections is particularly significant as showing the ineffectiveness of sodium alone, without an activator, to effect anysubstantial improvements.

EXAMPLE 4 As still another comparison of the use of sodium alone and sodium with an activator in the refining of an oil, a thermal naphtha distilling. in the range of225 to 400 F. was employed. In the case in which finely divided sodium alone was employed at 90 C. in a weight per cent of 0.75%, the sodium Similarly. when 10 mol per cent of isopropyl ether based on the sodium was employed, no appreciable refin ing efiect took place. This example again indicates that the ether does not act as an activator at temperatures of, or below 90 C.

EXAMPLE 5 A thermal naphtha boiling in the rangefl225 to 400 F. was employed having an initial sulfur content of 0.146% and having a deposit factor of 55. When this naphtha was treated with 1% of sodium having a particle size of 2 tot microns and 7.5 mol per cent of ethyl ether, it was found .thatthesuIfur content had been cut .down to 0.016%,andthe deposit factor-had dropped to 14.5.; This experiment therefore indicates that j ethyl ether as well as isopropyl ether is a suit ableactivator insodium refining. V i

EXAMPLE 6 Ina similar run again employing .a thermal naphtha havingthe inspections given in the for- ,,mer example and employing 1% of sodium activated with 10 mol percent of acetone, itwas found that the sulfur content was reduced to 017 and the deposit factor was reduced to 13 It is apparent irom these data that acetone serves irig Example 2 to Example 1, it will be noted that the presence of the ether at the higher refining temperature was responsible for material improvement in each of the inspections. This result was not due to the difference in refining as an activator in sodium refining.

EXAMPLE '7 Experiments were also conducted employing a heavy catalytic naphtha having a boiling range of 330 to 438 F. In each experiment 400 parts of this naphtha were agitated with 4 parts of the contents of the bomb were cooled below 50 C. l

and the sludge was removed by filtration. The

The reactants 17 'r'esultsoff-these-tests are indicated inthe followhag-table Y Mole Percent Actwatol Percent .Sulfur. DF

,Noircetln 0.385 .13. lsop opyl alcohol. 10 0.078 3.1 'l iButylaloohol 10 0.103 3. 5 --IsoproDY1 Ether 7. 5 0. 123 e. 0 .A cetone .Q... 0.108 c. 9

: ibiaaoniumifluoborate'deposit factor. 0

It isapparent fromthese data that each of the activators tested. is effective .to provide substantial refining efiects as indicated by the sulfur reduction andthe improvement in the diazonium fluoborate depositfactor.

'. EXAMPLEB 1r The :use of ethers. is particularly;advantageous :since: their concentration is not critical and they jma-y remain in the gasoline as valuable fuel com- ;ponents. The following data illustrate that'the concentrationof isopropyl ether is not critical. These data .arefrom runs using thermalnaphtha .with 1%ofsodi-um at 225 C. for one hour. The -sodium .wasas .a. dispersion of .2-6 microns in. a virgin. naphtha; of 320-380 ,F.. boiling range.

- Percent I Final Activator Activator 1 sulfur DFDF 2 v5- -t: a Is 1'0 Dfl-" (1011 23 .Do.--.--- 30 0.016 19 Ethyl Ether 7. 5 0. 016 I 14. 5

Mole percent. 1 ZDiazonium .fluoborate deposit factor.

' One run with; ethyl ether is also shown for comparative purposes. It may be noted that although dium' and about 5 to 30 mol 'per cent'of an activator based on the quantity of sodium, said activator bein a compound "selected from the group consisting of ethers and ketones.

crackedv gasoline fraction.

. 2.-;.-'1 he,process defined. by claim 1 in whichthe -.said-,finely dividedsodium consists of particles of sodium-smallersthan about 50 microns in di- -.ameter.

. 3. The process defined by claim 1 in which the said petroleum-oil. is a cracked gasoline fraction.

4. The rprocessof improving the oxidation stability and engine cleanliness of a cracked gaso- -line consisting of agitating the said. gasoline invliquid phase in contact with about 0.25 .to 2.0

.per. cent of sodium having particles less than .about 50-:microns in diameter and about 5 to 30 mol per cent, based on the sodium iof isopropyl qethergsaidsagitation being carried out-ata tem perature above C- and below about 250 \C.

.and thereafter cooling said mixture'and filtering below ..about.50- C. whereby a refinedgasoline is obtained.

The process .definedby claim 4 inwhioh thesaid-cracked gasoline consists of a thermally 1.6. The ,process defined by claim 4 in-which the said gasoline consists of a catalytical-lycracked gasoline fractions 7. The process according topclaiinlin which the. said temperature at whichagitation-is con- 7 .ducted is, in the range-of 200 t0u225 C 8. The process of improving the oxidation stability of a petroleum oil in which the said oil is contacted in liquid phase-with finely divided sovdiumand ,an aliphaticether having from 4,-to l0 carbon-,atoms said contact being carried outat temperatures above 150 C. the sodium being present in proportions ofrabout .5vto 1% based on a weight of .oil. being treated and saidetherbeing employed in proportions of-about .5 to- 10 :molal .1391 cent based onwthe quantity ofsodium' employed.

BYRON .M. VANDERBILT.

-REFERENCES CITED The following references .are'of record in the file of this patent:

UNITED STATES PATENTS Nu-r nbe'r Name Date 1,801,412 Ca'rlisle Apr. 21, 1931 1,938,670 Sullivan et a1. Dec..12,1933 1,939,839 Williams et al Dec. 19, 1933 FOREIGN PATENTS Number Country Date 392,142 Germany l Mar. 17, 1924 ..4l01,353 Germany .'Sept.-:2, 1924 

1. THE PROCESS OF IMPROVING THE OXIDATION STABILITY OF PETROLEUM OILS IN WHICH THE OIL TO BE TREATED IS MAINTAINED AT A TEMPERATURE ABOVE ABOUT 150* C. AND IS CONTACTED IN LIQUID PHASE WITH ABOUT 0.25 TO 2.0% OF FINELY DIVIDED SODIUM AND ABOUT 5 TO 30 MOL PER CENT OF AN ACTIVATOR BASED ON THE QUANTITY OF SODIUM, SAID ACTIVATOR BEING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ETHERS AND KETONES. 